Local authorities on Friday denied a second chlorine gas leak belching from a chemical plant that has already hospitalized 298 people in Tongzi county of Guizhou Province in southwestern China.

Eighty students from Yucai Middle School in the county were sent to hospital with poisoning from polluted air on Wednesday, suspecting a new leak from Zunbao Titanium Plant, according to a Friday report by the Guizhou City News.

A?student was sent to hospital with poisoning from polluted air on Wednesday.

The tragedy happened within a week of 106 students from Yuantian Primary School - 500 meters from the plant - being taken to hospital complaining of nausea, stomachache and chest distress on June 17, according to the report.

A county government official denied there was a second gas leak on Wednesday.

All four workshops in the plant have halted trial operations until Thursday, Linghu Shaohui, a deputy county chief in charge of large projects at the industrial base where the plant is located, told the Global Times on Friday.

"There's no second leak at the plant jeopardizing locals' health," he said.

A preliminary investigation showed the plant had discharged excess chlorine due to an equipment failure during its trial operation at 11:10 am on June 17.

But Deng Zifen, a student at Yucai Middle School said she and her classmates smelled something strange in their dorm, and were sent to hospital for further checks on Wednesday, according to the Guiyang-based Guizhou City News.

Some villagers told the newspaper they still smelled polluted air after the county government said they had stopped operations, suspecting the plant was still working when they saw trucks carrying poisonous substances to the plant.

"Some of my students are showing symptoms of nausea and chest pains five days after the accident," the newspaper quoted an anonymous middle school teacher as saying.

Luo Zhaoqi, a deputy chief of the county's health bureau told the Global Times that after the leak was exposed by the media on June 17, 401 people had gone for medical checks at the hospital so far. Two-hundred and ninety-eight stayed overnight for medical treatment.

"Only a few" of the villagers and students who went to the hospital needed treatment, Luo said.

Some 67 - mostly primary and high school students - were still being treated, Luo told the Global Times, all of them in a stable condition.

"The workshop where the accident happened stopped operations two days after the accident," said deputy county chief Linghu. "We've invited the environmental protection department to the site to monitor further developments and recently there have been no more poisonous gas leaks."

Water and soil near the plant had been sampled, and recent air monitoring showed chlorine levels were "under normal range," Linghu said.

Schools near the plant were shut until next Monday, but the reopening date will finally be settled after the environment is safe for students, county chief Zhang Yongkang told the Global Times on Friday.

Established in 2007, the plant owned by Zunbao Titanium is in trial operation manufacturing magnesium chloride and titanium. If the environmental standards were not met, they would consider shutting down the whole project, the deputy county chief added.

"We'll discuss the compensation plan for those hospitalized students and villagers after they get out of hospital as the number of people who are going for medical checks is constantly changing," Jiang Ankang, the labor union chief of the plant told the Global Times on Friday.

Jiang said the reopening date for the plant was still uncertain.

The Zunbao Titanium Plant is the star project of the local industrial base 40 kilometers from Zunyi and 180 kilometers from Chongqing.

Analysts said construction of plants near schools should be more carefully considered especially where pollution might be involved.